The invention concerns a method and an apparatus for data transmission between an electromedical implant and an external apparatus, as set forth in the classifying portion of claim 1 and the classifying portion of claim 13 respectively.
In order to monitor operation of an electromedical implant or the state of the patient in question, it is necessary for such implants to be equipped with telemetry devices. They make it possible for data which is available in the implant and which reflects the state of the patient and the implant to be read out into an external apparatus in a contact-free procedure. Such electromedical implants are for example cardiac pacemakers, defibrillators, cardioverters or other electronically actuated or controlled implants.
Thus U.S. Pat. No. 5,720,770 discloses for example a method of data transmission between an electromedical implant having a first transmitter/receiver unit and an associated external apparatus having a second transmitter/receiver unit, wherein data transmission begins with a triggering signal which is sent from the transmitter/receiver unit of the external apparatus to the transmitter/receiver unit of the implant. That triggering signal is sent at predeterminable first intervals of time, in normal operation of the implant. In such a bidirectional radio path as is used here, the receivers at both ends of the communication path are always switched on in order to detect when the other partner in the communication takes up a communication.
The energy resources within an electromedical implant of that kind however are severely limited so that it would be desirable to achieve the lowest possible level of energy consumption in order to increase the operating life.
For that purpose, U.S. Pat. No. 5,720,770 proposes that the processors which control the telemetry device of the implant are powered down to a minimum level of operation during the inactive times of the telemetry device and that they are “woken up” upon the receipt of a triggering signal from the external apparatus and go back up into the normal mode of operation in which more energy is consumed.
That method however still suffers from the disadvantage that the receiver of the implant must be continuously in operation in order to detect the triggering signal from the external apparatus.
Therefore the object of the invention is to provide a method of the general kind set forth, which permits energy-saving operation of the implant.